Blend films of natural wool and cellulose prepared from an ionic liquid

Transcription

1 Cellulose (2010) 17: DOI /s Blend films of natural wool and cellulose prepared from an ionic liquid Nishar Hameed Qipeng Guo Received: 15 September 2009 / Accepted: 17 February 2010 / Published online: 7 March 2010 Ó Springer Science+Business Media B.V Abstract Natural wool/cellulose blends were prepared in an ionic liquid green solvent, 1-butyl- 3-methylimidazolium chloride (BMIMCl) and the films were formed subsequently from the coagulated solutions. The wool/cellulose blend films show significant improvement in thermal stability compared to the coagulated wool and cellulose. Moreover, the blend films exhibited an increasing trend of tensile strength with increase in cellulose content in the blends which could be used for the development of wool-based materials with improved mechanical properties, and the elongations of the blends were considerably improved with respect to the coagulated films of wool and cellulose. It was found that there was hydrogen bonding interaction between hydroxyl groups of wool and cellulose in the coagulated wool/ cellulose blends as determined by Fourier transform infrared (FTIR) spectroscopy. The ionic liquid was completely recycled with high yield and purity after the blend film was prepared. This work presents a green processing route for development of novel renewable blended materials from natural resource with improved properties. Keywords Cellulose Wool Blends Ionic liquid N. Hameed Q. Guo (&) Institute for Technology, Research and Innovation, Deakin University, Geelong, VIC 3217, Australia qguo@deakin.edu.au Introduction The strong need for development of new eco-friendly materials has led people to focus on natural resources since the non-degradable plastics and their existing anti-natural processing methods have become a threat to the environment and are exhausting much limited petroleum resource. Moreover, one of the primary concerns of current polymer processing industry is the use of high volumes of volatile organic solvents as liquid media for polymer synthesis, extraction, and formulation. Recent regulatory controls have aggressively targeted the reduction of the volume of industrial pollutants, a major part of this comprise the careful material and solvent selection and a search for less harmful or recyclable alternatives. Therefore, increased attention is being paid on exploitation of naturally exiting polymers and their environmentfriendly processing techniques (Kaplan 1998; Klemm et al. 2005). Cellulose, which is the structural component of the primary cell wall of green plants, is the most common organic compound on the Earth. Cellulose is mainly obtained from wood pulp and cotton. Natural wool is another abundant natural material, which has evolved over thousands of years to insulate and protect sheep. It has been estimated that wool contains about 20 amino acids linked together in ladder-like polypeptide chains (Block et al. 1939). The insulating and moisture absorbing properties of wool make it into extremely comfortable textiles. It is noted that everyday large

2 804 Cellulose (2010) 17: amount of wool and different forms of cellulose are wasted during wool weaving, disposal of used cloths and paper wastes. Both cellulose and wool are renewable, biodegradable, and biocompatible, but difficult to process by directly dissolving into common solvents. This is due to the molecular close chain packing and various inter and intramolecular hydrogen bonding (Hames and Hooper 2003). It is well known that blending is an expedient technique for the development of new polymeric materials with improved properties (Guo 1999). The phase behavior and properties of polymer blends are highly dependent on the extent of intermolecular association. The existence of a favorable intermolecular interaction between two polymers can promote their miscibility and also has a significant effect on the properties of the blends. For functional applications and chemical modifications, it is essential to form a stable homogeneous wool or cellulose solution in order to improve the efficiency of the application. The production of regenerated cellulose material is based on a 100 year old viscose technology which is, however, accompanied by environmentally hazardous by-products (Garrett and Grisham 2002). Some other solvents are also developed to substitute this cellulose method and among them, the MMO/H 2 O system is the only industrialized, but also has disadvantages such as use of high temperature, degradation of cellulose, and its high cost (Garrett and Grisham 2002). Solvent systems like carbamide/h 2 O 2 /H 2 O and carbamide/2-mercaptoethanol were used for the processing of wool (Anastas and Warner 1998). The perceived harmful effects of all these solvents on human health, safety, and the environment combined with their volatility and flammability has lead to increasing pressure for minimizing their use both from a public relations and a cost perspective. Consequently, new processing strategies for developing potential applications of natural resources were under extensive investigation. The design of products and methodologies that reduce or eliminate the use and generation of hazardous substances comes under green chemistry (Phillips et al. 2004). Recently, ionic liquids (ILs) are attracting much attention for potential applications in various fields due to their unique physicochemical properties such as non-volatility, non-flammability, chemical and thermal stability and ease of recycling (Seddon 1999; Earle and Seddon 2000; Wilkes 2002; Novoselov et al. 2007; Zhang et al. 2006; Wilkes and Zaworotko 1992; Welton 1999; Dupont et al. 2002; Sheldon 2001; Wasserscheid and Keim 2000; Song 2004; Huddleston et al. 2001; Hoffmann et al. 2003; Davis and Fox 2003; Antonietti et al. 2004). In fact, the properties of ILs can be manipulated according to the requirements since they offer great flexibility in designing cationic and anionic structures and their combinations; therefore they have been termed the designers solvent. (Wilkes 2002) Ionic liquids possess exceptional solubility characteristics due to their special structures compared to the traditional molecular solvents. Swatloski et al. (2002) showed that cellulose can be easily dissolved in ionic liquids without the formation of any derivative. They prepared concentrated solutions of cellulose in 1-butyl-3- methylimidazolium chloride (BMIMCl) and cellulose can be regenerated by coagulation in water or ethanol. 1-allyl-3-methylimidazolium chloride (AMIMCl) is another highly efficient direct cellulose solvent developed by Zhang et al. (2005), Wu et al. (2004), Zhang et al. (2007) and they found that coagulated cellulose exhibited good mechanical properties. Many other recent works have been reported regarding the dissolution and regeneration of cellulose in different ILs (Kadokawa et al. 2009; Wu et al. 2009). Recently, Xie et al. reported the dissolution and solubility of wool keratin fibres in BMIMCl (Xie et al. 2005; 2006). In this paper we investigate the dissolution and blending of wool and cellulose in room temperature ionic liquids to obtain novel natural biopolymer blend materials. Natural wool/natural cellulose blend films were developed from 1-butyl-3-methylimidazolium chloride (BMIMCl). The hydrogen bonding interactions and the phase behavior were investigate using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The morphology of the blends was examined using scanning electron microscope (SEM). The thermal stability and crystallization was investigated using thermogravimteric analyzes (TGA) and wide angle X-ray diffraction (WAXD) methods. The mechanical properties of the blends were examined using tensile measurements. This work provides an example of natural polymer-blended biodegradable and renewable materials with improved properties using a single green solvent.

3 Cellulose (2010) 17: Experimental section Materials Natural raw wool, shorn from an Australian merino sheep, was cleaned using acetone/ethanol solvent mixture in a Soxhlet extractor for 48 h. Then it was washed several times with deionized water and finally dried in vacuum oven at 100 C for 15 h. Microgranular cellulose was purchased from Aldrich. The cellulose sample was dried at 80 C under vacuum for about 5 h to remove moisture. 1-butyl-3-methylimidazolium chloride (BMIMCl) was obtained from Fluka. The chemicals were used as received. Preparation of coagulated wool and wool/ cellulose blends The coagulated wool, cellulose and the blends were prepared in the following way. To obtain 5 wt% of wool solution in BMIMCl, about 1 g of wool was dispersed into 20 ml of BMIMCl in a 100 ml flask, and the mixture was heated at 100 C and stirred until wool samples were completely dissolved in 10 h to give a clear and viscous wool solution. To dissolve cellulose, 1 g of cellulose was mixed with 20 ml BMIMCl, heated and stirred at 100 C to obtain a 5 wt% completely homogeneous cellulose solution. The dissolved wool and cellulose could be coagulated in water as BMIMCl was completely miscible with water in any ratios. This can be done by pouring the viscous solution into excess of deionized water and coagulated several times. The individual coagulated wool and cellulose films were obtained by casting the viscous solution in between two glass plates and then soaked in the water bath to allow the ionic liquid to diffuse from the film. During the process, water should be changed several times to ensure that the IL is removed completely from the sample. After the washing with deionized water several times for the complete removal of the ionic liquid BMIMCl, the coagulated wool and cellulose films were then dried in a vacuum oven to get a brittle and flat blend films. The wool/cellulose blend films were prepared by the mutual mixing of wool/bmimcl and cellulose/ BMIMCl solutions together. This was done by taking different weight ratios of wool and cellulose in IL, dissolved them individually and mixed each other. For example, 80/20 wool/cellulose blends were prepared by making wool solution (0.8 g in 16 ml BMIMCl), cellulose solution (0.2 g in 4 ml BMIMCl) and mixed them together to get a total of 80/20 blends in 5 wt% solution. The mixture solution was stirred at 100 C again for 12 h in order to ensure the complete intermixing. Coagulated wool/cellulose blend films were obtained in the same way as that of coagulated wool. Even compositions i.e., 20/80, 40/60, 60/40, 80/ 20 wool/cellulose blends were prepared and characterized to study the changes in structure and properties with composition. Fourier transform infrared (FTIR) spectroscopy The FTIR spectra of all the samples were measured on a Bruker Vetex-70 FTIR spectrometer. The KBr disk method was adopted to conduct the FTIR experiments. The blend sample was mixed with KBR powder, ground well and prepared to KBr disks. The disks were dried under vacuum in an oven at 100 C before the measurements. The spectra were recorded at the average of 32 scans in the standard wavenumber range of 400 4,000 cm -1 at a resolution of 4 cm -1. The spectrometer was equipped with a DigiTech DLATGS detector with integrated preamplifier. The standard beam splitter was a Ge-based coating on KBR and the scanner velocity is 6 Hz. Differential scanning calorimetry (DSC) DSC experiments were carried out using a TA-DSC model Q200 instrument. The measurement was performed using 5 10 mg of the sample under an atmosphere of nitrogen gas. The samples were first heated to 100 C and held at that temperature for 5 min to remove the thermal history. Then the samples were cooled to 0 C at a rate of 20 C/min, held for 5 min, and subsequently heated from 0 to 250 C at 20 C/min (second scan). Glass transition temperature (T g ) values were taken as the midpoint of transition in the second scan of DSC thermograms. Wide-angle X-ray diffraction (WAXD) measurements X-ray diffraction was performed on a Philips-PW 1729 diffractometer with Cu KR radiation (k = Å) at 40 kv and 30 ma were recorded in the range of 2h = 5 40 with an X-ray diffraction. The

4 806 Cellulose (2010) 17: coagulated film samples were cut into strips of 10 mm long and 15 mm wide for the measurements. Thermogravimetry analysis (TGA) Thermogravimetry analyses (TGA) were performed on Netzsch STA 409 thermogravimetric analyzer over a temperature range of C at a heating rate of 10 C/min under nitrogen atmosphere. Scanning electron microscopy (SEM) The morphology of free surfaces of the blends was examined with a Leica S440 scanning electron microscope (SEM) at an activation voltage of 5 kv. The free surfaces were coated with thin layers of gold before the observation. Mechanical tests The tensile behavior of the blends was analyzed using a Lloyd LR 30 K testing machine in tensile mode with a load cell of 100 N capacity with a gauge length of 5 mm. The specimen was a thin rectangular strip ( mm). The load displacement curves of the samples were obtained at room temperature at a strain rate of 1 mm/min. The stress and strain values were obtained using the standard equations. The samples were kept at 100 C for 15 h before the tests and experiments were repeated with 5 samples of each composition. The tests were performed at 75% relative humidity and 20 C temperature. Results and discussion Phase behavior and morphology The photograph of the wool/cellulose blend film coagulated from BMIMCl is shown in Fig. 1. The phase behavior of wool/cellulose blends was investigated using DSC. The DSC curves of the second scan of the blends with various compositions are shown in Fig. 2a. Coagulated wool shows a T g of 156 C as can been from the figure. From the literature, the T g of cellulose in dielectric, NMR and other studies is described to be in the region C (Kubat and Pattyrante 1967; Nishiyama et al. 2002). However, T g of coagulated cellulose could not be examined in our Fig. 1 Photograph of the 40/60 wool/cellulose blend film prepared from BMIMCl. The diameter of the film sample is ca. 45 mm DSC experiments. The wool/cellulose blends show a single T g corresponding to the wool rich phase which broadens and shifts towards higher temperature region as the concentration of cellulose increases. This could be due to the partial miscibility of wool with cellulose in their coagulated form. At higher concentrations of cellulose, T g curve disappears. The shift in T g values of the wool-rich phase indicates the miscibility in these polymer mixtures. The T g -composition diagram of the wool/cellulose blends is shown in Fig 2b. The X-ray diffraction studies of wool/cellulose blends were performed and the results are shown in Fig 3. Actually, original cellulose shows a diffraction peak 2h = 14.8, 16.3, and (not shown for brevity). In coagulated cellulose a transformation from cellulose I to cellulose II has been occurred which is identified by the shift in peaks to 20.3 and Zhang et al. (2005) also reported the same shift in peaks. The same observation was also reported in the dissolution procedures of cellulose with other known solvent systems. However, it can be seen that the peaks at 14.8 and 16.3 collapsed to form a single broad peak. Moreover, the intensity of the crystalline peaks is reduced considerably in coagulated cellulose. This can be attributed to the low degree of crystallinity of cellulose as the dissolution process in ILs resulted in the breakdown of intermolecular hydrogen bonding. The coagulated wool has not shown any strong diffraction peak. However, a low intense diffraction peak was observed around 208. This may be due to the transformation of crystalline to

5 Cellulose (2010) 17: Fig. 2 a DSC thermograms, and b T g -composition plot of wool/cellulose blends a 100/0 80/20 wool/cellulose b 250 Endo 60/40 40/60 20/80 0/ C 175 C 193 C 199 C Temperature ( C) T g blends 208 C Temperature ( C) Cellulose (wt%) Intensity (a.u.) 20/80 40/60 60/40 80/20 100/ theta wool/cellulose 0/100 Fig. 3 WAXD patterns of wool/cellulose blends amorphous form after dissolution in BMIMCl. In wool/cellulose blends, the cellulose crystallization peak becomes less and less intense as the concentration of wool increases. This could be due to the decrease in crystallinity of the coagulated cellulose owing to the formation of hydrogen bonds with wool. The morphology of the wool/cellulose blends were investigated using SEM. The morphology of pure wool fibers, coagulated wool, cellulose and coagulated cellulose are given in Fig. 4. As can be seen, the morphology of the coagulated wool and cellulose are significantly changed. Both the regenerated wool and cellulose show a relatively diffused texture (Fig. 4b, d). Rogers and co-workers (Swatloski et al. 2002) previously revealed that the regenerated cellulose fibers showed a diffused fibrous morphology in which the fibers fused into a conglomerate texture rather than a homogeneous film. Similarly, the regenerated wool (Fig. 4b) and wool/cellulose blends (Fig. 5) in this study also show a diffused fibrous morphology. Figure 5 represents the SEM micrographs of the free surfaces of regenerated wool/cellulose blend films. The heterogeneous morphology was observed in 80/20 to 60/40 wool/cellulose blends. However, there is no obvious evidence of inhomogeneity observed in blends containing very high concentrations of cellulose (80/20). SEM image of coagulated wool/ cellulose blends containing 20 and 40 wt% cellulose are given in Fig. 5a, b, respectively. It can be observed that these blends are not homogeneous displaying characteristics of a phase separated structure. The high wool content can be observed in these compositions and wool appears to be the major phase in these blends. With increasing cellulose content, the morphology of the blend films changed dramatically. The wool/cellulose blend with 60 wt% cellulose gives rise to obviously different phase separated morphology, i.e., wool-rich and cellulose-rich phase can be easily discerned. This is

6 808 Cellulose (2010) 17: Fig. 4 Scanning electron micrographs of a pristine wool fibers, b wool coagulated from BMIMCl, c pristine cellulose, and d cellulose coagulated from BMIMCl Fig. 5 Scanning electron micrographs of a 80/20, b 60/40, c 40/60, and d 20/80 wool/cellulose blends also schematically shown in Fig. 5c. As the concentration of cellulose again increases, the blends become homogeneous to some extent as there is no apparent indication for phase separation in 20/80 wool/cellulose blends (Fig. 5d). This could be due to the insertion of wool-rich phase within the

7 Cellulose (2010) 17: cellulose-rich phase which is comparatively higher in concentration. The SEM surface morphology of the blends shown in Fig. 4 is more or less like a composite. However, the FTIR and DSC prove there is hydrogen bonding interaction between hydroxyl groups of wool and cellulose and thereby partial miscibility between the components. Hydrogen bonding interactions and phase behavior Cellulose is derived from D-glucose units, which condense through glycosidic bonds (Crawford 1981; Updegraff 1969). The multiple hydroxyl groups on the glucose residues holding the chains firmly together side-by-side and forming microfibrils with high tensile strength. Wool is a natural fiber composed of keratintype protein that grows from the follicles of the sheep s skin. (Kaplan 1998) Chemically these proteins contain five elements: carbon, hydrogen, oxygen, nitrogen and sulphur which are combined into amino acids. It is known that wool contains more than 20 amino acids linked together. The structure and chemical nature of wool have been studied extensively. (Rippon 1992; Morton and Hearle 1993; Rippon 2003) The chief elements include nitrogen, sulfur, amino acids including cysteine, arginine, glycine, etc. The three-dimensional structure of wool involves intermolecular hydrogen, ionic, and physical forces of attraction and importantly, the sulphur containing disulphide bonds, which make keratin fibers insoluble in most of the solvents and more stable to chemical and physical attack than other types of proteins. (Block et al. 1939) Therefore, in order to dissolve wool and cellulose, these inter and intramolecular interactions have to be disrupted. It is reported that high chloride concentration in BMIMCl is highly efficient in breaking down the highly networked hydrogen bonding and thereby dissolving these natural polymers (Swatloski et al. 2002). In the case of wool, the dissolution of wool could be occurred due to the rupture of disulphide bonds in IL. However, further investigation by using some more effective characterization techniques, such as NMR and Raman spectroscopy, is still needed to prove the mechanism of dissolution of wool in ILs. Both wool and cellulose contains many functional groups where both proton accepting and donating groups present. BMIMCl exists as dissociated BMIM? and Cl - ions under heating. The free Cl - anions complexed with hydroxyl protons of wool and cellulose and the free BMIM? cations associated with hydroxyl oxygen. Such a complex association would disrupt the hydrogen bonding and lead to the dissolution in BMIMCl solution. A homogeneous solution is formed upon the mutual mixing of wool/ BMIMCl and cellulose/bmimcl. The relatively good interaction in this composition can be expected due to the increased capability of the two polymers, each with abundant hydroxyl groups, to interact mutually through hydrogen bonding. Hydrogen bonding interactions in polymer blends can be revealed using FTIR spectroscopy. The hydroxyl region in the FTIR spectra of wool/cellulose blends coagulated from BMIMCl is given in Fig. 6. The coagulated cellulose shows a broad band at 3,410 cm -1 which due to the presence of O H vibrations in the cellulose as verified by Zhang et al (2005). For the plain coagulated wool, the broad peak at 3,400 cm -1 is due to the self-associated hydroxyl groups collectively from the amino acids and the comparatively sharp peak at 3,280 cm -1 can be attributed to the stretching vibrations of N H groups. Absorbance (a.u.) wool/cellulose 100/0 80/20 60/40 40/60 20/80 0/ cm cm Wavenumber (cm -1 ) 3280 cm -1 Fig. 6 Hydroxyl stretching region in the infrared spectra of wool/cellulose blends

8 810 Cellulose (2010) 17: (Slark and Hadgett 1999; Church and Millington 1996) In the general secondary structure of a protein, the a-helix is a right- or left-handed coiled conformation, in which every backbone N H group is hydrogen bonded with the backbone C = O group of the amino acid. The peak at 3,280 cm -1 can be attributed to this hydrogen bonding. In the blends, the relative intensity of the peak corresponding to N H groups in wool (3,280 cm -1 ) decreases without any shift as the concentration of wool deceases. However, the self-associated hydroxyl band at 3,400 cm -1 changes its position upon blending. As the concentration of cellulose increases in the blends, the peak corresponding to the hydrogen bonded hydroxyl groups (3,400 cm -1 ) broadens and shifts towards lower wavenumber region. The peak at 3,340 cm -1 of 60/40 wool/cellulose blends corresponds to the hydrogen bonding interaction between hydroxyl groups of wool and cellulose. The peak shift is very much clear that it cannot simply be attributed to the proportional summation of the spectral envelopes of the pure polymer components. The FTIR spectra of the wool/cellulose blends in the region 2,000 1,200 cm -1 are given in Fig. 7 where the characteristic amide bands of the wool can be observed. The amide I band is observed in 1,680 and 1,645 cm -1 region and the amide II bands are at 1,550 and 1,515 cm -1 region. It can be seen from Fig. 7 that these bands exist in coagulated wool and all wool/cellulose blends. However, the intensity of amide bands decreases as the concentration of wool decreases in the blends. Absorbance (a.u.) wool/cellulose 0/100 20/80 80/20 60/40 40/60 100/0 Amide I Amide II Wavenumber (cm -1 ) Fig. 7 FTIR spectra of the wool/cellulose blends in the region 2,000 1,200 cm -1 Stress (MPa) wool/cellulose 0/100 20/80 80/20 60/40 100/0 40/60 Mechanical properties and thermal stability The stress strain curves of wool/cellulose blend films coagulated from BMIMCl are shown in Fig. 8. The Young s modulus, maximum tensile strength and elongation at break are shown in Table 1. The coagulated cellulose showed highest Young s modulus value of about 2.4 GPa and the modulus is least for coagulated wool 0.9 GPa. Apparently the modulus gradually increased with increasing cellulose content in the blends. Tensile strength (r b ) and elongation at break (e b ) are important mechanical properties of the wool/cellulose blend films, which mainly depend on components in the film and interfacial adhesion between them. It can be seen that the plain coagulated wool shows the lowest tensile strength of 25 MPa and Strain (%) Fig. 8 Stress-strain curves of wool/cellulose blends the coagulated cellulose shows a high tensile strength &54 MPa. From Fig. 8 and Table 1, it can be observed that the tensile strength of the blends increases with increase in cellulose content. The elongation at break (e b ) of the blends improved a little. The maximum value (e b = 9.8) is shown by 40/60 wool/cellulose blends which has also comparably good tensile strength (r b = 36 MPa) with other

9 Cellulose (2010) 17: Table 1 Tensile properties of wool/cellulose blend films prepared from BMIMCl Wool/ cellulose (wt%) Young s modulus (GPa) Tensile strength (MPa) Elongation at break (%) 100/0 0.9 ± ± ± / ± ± ± / ± ± ± / ± ± ± / ± ± ± 1.1 0/ ± ± ± 0.6 blends. The variation in elongation at break could be due to the inhomogeneities in the blends at other compositions as revealed by SEM (Fig. 5). The morphology and the mechanical properties of the blends can be compared. The tensile strength shows an increasing trend with blends containing high cellulose concentration which is due to the high mechanical properties of cellulose compared to wool. The 40/60 wool/cellulose blend shows better elongation and reasonable tensile strength has obvious phase separated morphology with wool-rich and celluloserich phase (Fig. 5c). However, blends containing more wool content have poor mechanical properties which are more inhomogeneous (Fig. 5a, b). 238 C wool/cellulose The thermal decomposition behavior of the wool/ cellulose blends coagulated from BMIMCl was performed. The TGA curves of coagulated wool/cellulose blends are given in Fig. 9. The onset decomposition temperatures of plain coagulated wool and cellulose are 238 C and 270 C, respectively. It can be observed that the blends at higher cellulose compositions show higher decomposition temperature (T d ) than the plain solubilized-coagulated wool and cellulose. In fact, the T d of coagulated wool/cellulose blends increases with increase in cellulose content in the wool. However, the maximum thermal stability was exhibited by blend containing 40/60 coagulated wool/cellulose blends (298 C) and the value is 60 C and 28 C higher than plain coagulated wool and cellulose, respectively. Thus considerable improvement on thermal stability of wool can be attained through the blending with cellulose in IL media. Xie et al. (2005) observed that the thermal stability of coagulated wool keratin is slightly superior to that of natural wool keratin fibers. It is also reported that crystalline phase of wools was destroyed during the dissolution process in IL and could not be regenerated. On the other hand, regenerated cellulose exhibits a lower onset temperature for decomposition as reported by Swatloski et al. (2002) Here, the enhanced thermal stability of the blends can be attributed to the strong interaction between wool and cellulose facilitated by the IL media as revealed by FTIR study. Ionic liquid recycling Mass % (a.u.) 246 C 261 C 298 C 275 C 270 C 100/0 80/20 60/40 40/60 After the coagulation of wool/cellulose blend films, the residual BMIMCl in coagulation bath was recovered by the distillation of the water/bmimcl mixture under reduced pressure both in rotary evaporator and distilling apparatus as described by other authors (Zhang et al. 2005; Wu et al. 2004). Conclusions Temperature ( C) Fig. 9 TGA curves of wool/cellulose blends 20/80 0/100 In this study, we have successfully prepared novel wool/cellulose blend films in BMIMCl coagulated with water. The blending with cellulose can contribute significantly to the improvement in thermal stability of the wool and the blends give significantly higher thermal stability than the individual components. Moreover the blends showed comparable

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